1. Field of the Invention
The present invention relates to a particulate measurement system which measures the amount of particulates such as soot contained in a gas.
2. Description of the Related Art
Conventionally, a particulate measurement system has been known which measures the amount of particulates such as soot contained in exhaust gas discharged from an internal combustion engine such as a diesel engine (Patent Documents 1 and 2). This particulate measurement system generates ions by means of corona discharge, electrifies particulates contained in the exhaust gas by the generated ions, captures ions not used for electrification of particulates, and measures the amount of particulates contained in the exhaust gas based on the amount of trapped ions (in other words, based on the amount of ions used for electrification of particulates that were not trapped). The amount of trapped ions correlates with the amount of ions used for electrification, and the amount of ions used for the electrification correlates with the amount of particulates contained in the exhaust gas. Therefore, the particulate measurement system can measure the amount of particulates contained in the exhaust gas flow from the amount of trapped ions.    [Patent Document 1] Japanese Patent Application Laid-Open (kokai) No. 2012-220423    [Patent Document 2] Japanese Kohyo (PCT) Patent Publication No. 2012-194078
3. Problems to be Solved by the Invention
The present inventors found that the relation between a measurement signal representing a current corresponding to the above-described amount of ions and the amount of particulates changes in accordance with specific operating conditions of an internal combustion engine and a vehicle, such that the resulting measurement accuracy is low.